Senate Agriculture members grilled high-ranking leaders of USDA and the Office of the U.S. Trade Representative during a hearing Thursday over the Trump administration's trade policies and the resulting harm to farmers from retaliatory tariffs.

Both Republicans and Democrats on the panel gave an earful to USDA chief economist Robert Johansson, Undersecretary for Trade and Foreign Agricultural Affairs Ted McKinney, and USTR's chief agricultural negotiator Gregg Doud.

The common theme of the questions: When will the trade pain end for ag producers?

"It seems like the light at the end of the tunnel is a train coming at my farmers," said Sen. Joe Donnelly (D-Ind.), who's seeking reelection this November in one of the year's tight races. "They need to know that there's an off-ramp, or an end to this."

"The concern and anxiety level is continuing to rise in farm country," said John Thune of South Dakota, the third-highest ranking Senate Republican. "My impression is it seems to fall on deaf ears around here."Aside from the bipartisan angst from farm-state lawmakers, the hearing produced some new details from Doud about ongoing trade negotiations.

Here's a rundown of the highlights from reports by Liz and Pro Trade's Doug Palmer:

TPP: Top Republicans asked about rejoining the 11-member Trans-Pacific Partnership. Doud said Trump is correct to prefer a bilateral approach. "I've heard that now for the last couple of years, since we decided to pull out of TPP, that we're working on bilateral trade agreements," Thune said. "But I don't see any evidence that we are."

Ag is a must-have: Doud said U.S. Trade Representative Robert Lighthizer stressed to his counterpart this week that trade talks between the U.S. and EU must include agricultural issues, even if it is tough for the bloc's member nations to yield on the issue. He also criticized China at length over its ag barriers and tariffs, Doug wrote.

Canadian milk: Ending Canada's Class 7 milk pricing program (a recent classification created for certain milk protein byproducts that are used in goods like cheese and yogurt) is the primary focus of dairy discussions between the U.S. and Canada, Doud said. U.S. officials contend Canada's practices dried up demand for U.S. milk protein and encouraged Canada to dump its excess on the world market in violation of international trade rules.